Means for reducing fuel delivery of fuel injection pumps in the low rpm range

ABSTRACT

In a fuel injection pump in which the fuel quantities delivered for injection are controlled by bypassing one part of the fuel from the pump work chamber during the pressure strokes of the pump piston by a control edge of a slidable member that controls a bypass channel in an rpm-dependent manner, for reducing the delivered fuel quantities in the low rpm range at any load condition, said bypass channel is first opened by a throttle and subsequently opened by said control edge.

United States Patent [191 Faupel et al.

[111 3,827,832 [4 Aug. 6, 1974 MEANS FOR REDUCING FUEL DELIVERY OF FUELINJECTION PUMPS IN THE LOW RPM RANGE [75] Inventors: Werner Faupel,Gerlingen; Karl Zibold, Stuttgart-Vaihingen, both of Germany [73]Assignee: Robert Bosch GmbH, Stuttgart,

Germany [22] Filed: Oct. 18, 1972 21 Appl. No.2 298,761

[30] Foreign Application Priority Data Oct. 19, 1971 Germany 2151884July 14, 1972 Germany 2234557 [52] US. CL... 417/289, 123/139 AD,123/139 AY, 417/293, 417/494 [51] Int. Cl. F02m 59/34 [58] Field ofSearch .Q 417/289, 494, 293; 123/139 AD, 139 AM, 139 AY, 140 FG,139

[56] References Cited UNITED STATES PATENTS 2,547,174 4/1951 Rogers417/493 X 2,696,786 12/1954 Fleck et al. 417/499 3,044,404 7/1962Bessiere 417/293 3,168,042 2/1965 Bessiere 417/293 3,552,889 l/197lCurran et al... 417/494 3,614,270 10/1971 Franke et al.. 123/140 FG3,644,064 2/1972 Eckert et al. 417/293 FOREIGN PATENTS OR APPLICATIONS1,026,274 4/1966 Great Britain 417/293 Primary Examiner-Carlton R.Croyle Assistant Examiner-Richard Sher Attorney, Agent, or Firm-Edwin E.Greigg [5 7] ABSTRACT In a fuel injection pump in which the fuelquantities delivered for injection are controlled by bypassing one partof the fuel from the pump work chamber during the pressure strokes ofthe pump piston by a control edge of a slidable member that controls abypass channel in an rpm-dependent manner, for reducing the deliveredfuel quantities in the low rpm range at any load condition, said bypasschannel is first opened by a throttle and subsequently opened by saidcontrol edge.

9 Claims, 8 Drawing Figures munznws 61914 f 3.827. 832

SHEET 1 0F 4 Fig.1

PATENTEMus SIHM SHEET 3 BF 4 Fig.4

PAIENHU AUG 61874 saw an 4 BACKGROUND OF THE INVENTION This inventionrelates to a fuel injection pump for internal combustion engines and isof the type in which the delivered fuel quantities are altered as afunction of the rpm. The delivered fuel quantities are determined byinterrupting the fuel delivery at a certain, rpmdependent moment duringeach pressure stroke of the pump piston by means of opening a bypasschannel of the pump work chamber. The opening of the bypass channel iseffected by a control edge of a fuel quantity regulating member, such asa regulator shuttle or a control sleeve.

In internal combustion engines the smoke generated in the low rpm rangeunder full load conditions is caused by an imperfect combustion of thedelivered fuel quantities. Accordingly, a number of attempts havealready been made to adapt the fuel quantities to the actualrequirements of the engine. In particular, a reduction of the injectedfuel quantities in the low rpm range is sought after.

In a known fuel injection pump of the aforenoted type, such asdisclosed, for example, in U.S. Pat. No. 3,620,648 (German PublishedPatent Application DOS 1,947,528), in addition to a first bypasschannel, there is provided a second bypass channel which is opened bythe regulator shuttle prior to opening the first bypass channel. As longas no fluid abutment is present, however, this second bypass channel isclosed by a means provided on the pump piston before it could be openedby the regulator shuttle. As the fluid abutment increases, the secondbypass channel is opened to an increasing degree (the fluid abutmentwill be defined and explained later). The control edge for controllingthe second bypass channel is preceded by a further control point whichis formed as a throttle. In the beginning stage of the fluid abutment adischarge may occur only through this last-named throttle and only upona further displacement of the control plunger will the second bypasschannel be fully opened. By means of such an arrangement the injectedfuel quantities are reduced in the partial load range and in idling andthere is further achieved a smooth transition from the unaffected fullload range to the partial load range.

For an optimal operation of an internal combustion engine, it is,however, a requirement to inject at any load condition only that amountof fuel which is, in fact, required by the engine. Stated differentlyand as noted earlier, the injected fuel quantity has to be adapted tothe actual requirements of the engine. This applies in particular to thelow rpm range in which the vehicle engine operates for a substantialproportion of its entire operating period.

In a further known fuel injection pump of the abovedescribed type, suchas disclosed, for example, in U.S. Pat. No. 3,405,700 (German PublishedPatent Application DAS 1,526,500), the adaptation is achieved byangularly adjusting, by means of a sliding setting member which has ahelically extending control edge for opening the bypass channel. Theaforenoted setting memher, in turn, is shifted by the rpm-dependentpressure in the suction chamber of the fuel injection pump. Thisdisplacement of the setting member is effected against the force of oneor several springs of different rigidity. In this manner anrpm-dependent adaptation of the injected fuel quantities is achieved,whereby the accuracy of the adaptation depends upon the number of thesprings and the possibilities of gradation regarding the stiffness ofthe springs. This type of adaptation, however, results in substantialadditional costs.

OBJECT, SUMMARY AND ADVANTAGES OF THE INVENTION It is an object of theinvention to provide an im proved fuel injection pump of theaforeoutlined type in which under any load condition an rpm-dependentadaptation of the injected fuel quantities is achieved in the low rpmrange with simple means.

Briefly stated, according to the invention the bypass channel is firstopened by a control means formed by a throttle and then opened by theconventional control edge of a sliding member. The throttle is providedeither adjacent the mouth of the bypass channel on the componentcontaining the latter or on the slidable regulator member adjacent thecontrol edge.

The aforeoutlined arrangement has the substantial advantage that bymeans of an only slight structural change, the fuel quantities to beinjected are decreased in the lowest rpm range to an extent dependentupon the design of the throttle. In case of a high rpm, the throttleexerts, by virtue of the more pronounced throttle effect, no substantialinfluence on the injected fuel quantities. In case of a low rpm, thedecrease of the injected fuel quantities is stronger for partial loadthan for full load. In this manner the generation of smoke in the lowerrpm range is avoided and there is achieved a quiet run of the internalcombustion engine, particularly in the idling and in the partial loadrange.

The invention will be better understood, as well as further objects andadvantages will become more apparent, from the ensuing specification offour exemplary embodiments taken in conjunction with the drawmg.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a sectional schematic view ofa first embodiment of the invention illustrating a distributor-type fuelinjection pump in which the fuel quantity regulation is effected by theprinciple of fuel abutment";

FIG. 2 is a development of the control edges of the fuel quantityregulator member according to the first embodiment of the invention;

FIG. 3 is a fragmentary cross-sectional view of one componentillustrated in FIG. 1;

FIG. 4 is a development of the control edge of a regulator memberaccording to the second embodiment of the invention finding applicationin a fuel injection pump according to FIG. 1;

FIG. 5 is adevelopment of the control edge of a regulator memberaccording to the third embodiment of the invention;

FIG. 6 is a diagram of the course of the injected fuel quantities perstroke as a function of the pump rpm for different throttle designs;

FIG. 7 is a simplified sectional view of a fourth embodiment of theinvention finding application in a distributor-type fuel injection pumpin which the fuel quantity regulation is effected by a control sleevearranged on the pump piston and FIG. 8 is a fragmentary elevational viewof the pump piston illustrated in FIG. 7.

DESCRIPTION OF THE EMBODIMENTS Turning now to FIG. 1, a pump piston 1 ofa fuel injection pump operates in a cylinder 2 and is driven in such amanner by known means, not illustrated, that it executes a reciprocatingaxial motion and a rotary motion about its axis. The reciprocatingmotion serves for fuel delivery, while the roarty motion serves for fueldistribution. During the rotary motion, during the pressure strokes,fuel is admitted in sequence to the individual pressure conduits 3 (onlyone shown) which are arranged uniformly spaced about the cylinder 2. Ineach of the pressure conduits 3 there is situated a check valve 4. Onthe lateral surface of the piston 1 there is provided an axiallyparallel distributor groove 5 which, during each successive pressurestroke of the piston, connects the pump work chamber 6 with anotherpressure conduit 3. The pump work chamber 6 is supplied with fuelthrough a channel 7, an annular groove 8, one of longitudinal grooves 9provided on the lateral surface of the piston l, and a supply channel 10which communicates with a suction chamber 11. The latter,

in turn, is supplied with fuel by means of a fuel delivery pump 12 whichmay be a gear pump driven by the engine that is served by the fuelinjection pump.

In order to maintain an rpm-dependent pressure in the suction chamber11, the latter is connected with the suction channel 13 at the intakeside of the delivery ber 11. As the rpm increases, the piston plunger 16is displaced against the force of a return spring 17. As a result, theflow passage section of the throttle 15 is increased.

For the quantity control of the fuel delivered by the piston l to theengine during the pressure strokes, there is provided a regulatorshuttle 18. The latter controls a bypass channel 19a, 19b by controllingin an annular space 20 communication between the bypass channel portion19a and the bypass channel portion 19b. The bypass channel 19a, 19bleads from the pump work chamber 6 to the suction chamber 11. The bypasschannel portion 19a is in continuous communication with the annularchamber 20 in every position of the regulator shuttle 18. The bypasschannel portion 19b is connected with the suction chamber 11 through achannel 2]. A regulator spring 22 seeks to maintain the regulatorshuttle 18 in its position of rest which is determined by thecooperation of a solid fixed abutment 23 forming part of the pumphousing and a collar 24 affixed to the regulator shuttle 18. In thisposition of rest the latter maintains the bypass channel portion 19bclosed.

For the purpose of moving the regulator shuttle 18 away from itsabove-described position of rest, there is provided an auxiliary piston25 which operates synchronously with the piston 1 and which ispreferably formed as a stepped piston portion of the piston l. Theauxiliary piston 25 displaces fuel from its cylinder throughlongitudinal grooves 26 arranged on the lateral face of the piston 25and a channel 27 which contains a check valve 28 and which opens into acylinder 29 accommodating the regulator shuttle 18. Thus, by virtue ofthe fuel pressure generated immediately to the left of the regulatorshuttle 18 by the auxiliary piston 25, the regulator shuttle 18 isdisplaced towards the right against the force of the spring 22, wherebyhydraulic communication is established between the bypass portions 19aand 19b.

During the period between two pressure strokes of the piston 25, theregulator shuttle 18 returns to its position of rest, driven thereintoby the spring 22. During this return motion the regulator shuttle l8displaces one portion of the fuel present in the cylinder 29 through achannel 31 in which there is disposed a regulator throttle 30 brakingthe return motion of the control shuttle 18. The free flow passagesection of the regulator throttle 30 is adjustable by a throttle needle32 or the like. At a given flow passage section above a determined pumpspeed (that is, engine rpm), a fluid abutment appears which means thatthe regulator shuttle 18 does no longer return to its fixed position ofrest at the end of its return motion. Stated differently, the startingand terminal point of the reciprocating motion of the regulator shuttle18 will be spaced from its fixed position of rest and will shift to theright (towards the spring 22) as the rpm further increases. In thismanner the fuel quantity which is delivered during each pressure strokeof the pump piston to the fuel injection nozzles through the pressureconduits is decreased.

If the throttle 30 is widened, for example, during full load or partialload, then the initial and terminal point of the reciprocating motion ofthe control shuttle 18 shifts in an opposite direction (that is, towardsthe left) until the control shuttle 18 again engages the abutment 23.If, on the contrary, the flow passage section of the throttle 30 isdecreased corresponding to a lower partial load or zero load, then thestarting and terminal point of the reciprocating motion of the controlshuttle 18 travels correspondingly faster in the direction of theregulator spring 22. The maximum excursion of the control shuttle 18 isobtained when the latter opens 0 with its trailing edge a bypass channel34 which directs the residual fuel quantity displaced by the piston 25into the suction chamber 11.

The annular chamber 20 is bounded by a control edge 35 adjacent whichthere is disposed a control means 37 constituted by a throttle 36 bymeans of which, in the working position of the control shuttle 18, thechannel 19b is opened earlier than it is by the control edge 35. Thus,when viewed in the direction of shuttle travel caused by the fuelpressure in the cylinder 29, the throttle 36 is disposed immediatelydownstream of the control edge 35. In this manner, even before thecontrol edge 35 reaches the channel 19b, fuel is already drained fromthe pump work chamber, whereby the entire injected fuel quantity isdecreased. The faster the opening step occurs as the rpm increases, thestronger will be the throttle effect, so that in case of a high rpm, itis substantially only the control edge 35 which determines the moment ofopening the channel 19b.

In order to obtain an excess fuel quantity for starting the engine, thecontrol shuttle 18 has at its land portion which is remote from theregulator spring 22, a longitudinal groove (starting groove) 38 which,when the control shuttle 18 is rotated by means not shown, establisheshydraulic communication between the cylinder 29 and the bypass channel34. In this manner, during the phase of engine start, the fuel deliveredby the auxiliary pump 25 flows through the channels 34, 21 into 5. thesuction chamber 11 withoutdisplacing the regulator 18. Thus, in thisoperational condition the throttle 36 is inoperative. In thisembodiment, the throttle 36 is, with regard to the starting groove 38,so positioned adjacent the control edge 35 that in the rpm range whichimmediately follows the starting phase, the bypass channel portion 19bis not opened prematurely.

For the purpose of completely interrupting fuel delivery during theoperation of the fuel injection pump, the regulator shuttle 18 has atits land portion oriented towards the regulator spring 22, alongitudinal groove 39 (cutoff groove) which, upon proper angulardisplacement of the regulator shuttle 18, establishes communication, ina manner known by itself and therefore not shown here, between theannular chamber 20 and the bypass channel portion 1%. As a result, theentire delivered fuel is directed through the channel 21 into thesuction chamber 11, thus bypassing the pressure conduits 3.

. Turning now to FIG. 2, there is shown a development of the regulatorshuttle 18 with the cutoff groove 39, the starting groove 38, as well asthe throttle 36 constituting the control means 37. The throttle 36 isconstituted by a ground portion 360 extending parallel to the controledge 35 and axially bounded thereby. The ground portion 36a has a widthb and a depth t, as illustrated in FIG. 3. Instead of the ground planarportion 36a shown in section in FIG. 3, the throttle 36 may be of anyother shape; for example, it may be of annular configuration. It isapparent from FIG. 2 that in the absence of the throttle 36a theregulator shuttle 18 would start to open the bypass channel portion 1%only after a shuttle stroke s, while in the presence of the throttle 36such opening already starts after a shorter shuttle stroke s.

As the fluid abutment increases (that is, it travels to the right asviewed in FIG. 1), the stroke s decreases and thus there is also adecrease in the width of the sealing piston land between the bypasschannel portion 19b and the annular chamber 20. The thus appearingleakage losses in the lower rpm range reduce the injected fuelquantities, so that under partial load conditions there will be astronger adaptation of the fuel quantities than in case of full loadand, in particular, there is attained a silent idling of the engine.

FIG. 6 illustrates schematically how the throttle 36 affects theinjection quantity Q at different rpms. The curve formed of curveportions Q and 0,, corresponds to a regulator shuttle without athrottle; the curve portion 0,, illustrates the excess fuel quantity forstarting. Dependent upon the size and shape of the throttle 36, thereare obtained different curve portions such as O O82! O adjoining thecurve portion Q The curve portion 0,, is obtained from the curve 0, if,for example, in the throttle 360 the depth t of the ground portion isincreased. 0, is obtained from the curve Q81 if, for example, in thethrottle 36a the width b of the ground portion is enlarged.

The throttle 36 may be formed as an annular groove 36b which is incommunication in a tangential direction through the cutoff groove 39with the annular chamber 20 as shown in the developed illustration ofFIG. 4.

FIG. 5 shows a development of a regulator shuttle wherein adjacent thecontrol edge 35 there is provided a throttle in the form of a radialbore 360 which effects communication with the annular chamber 20 throughan axial bore 40.

In FIG. 7 there is schematically illustrated a fuel injection pump inwhich the injected fuel quantity is determined by means of a controlsleeve. In a cylinder 102 provided in the housing of a fuel injectionpump there operates a pump piston 101 which is driven by known andtherefore not illustrated means in such a manner that it executes anaxial reciprocating motion and a rotary motion about its axis. Thereciprocating motion serves for fuel delivery, while the rotary motionserves for fuel distribution. As a result of the rotary motion, duringthe pressure strokes, fuel is admitted sequentially to the individualpressure conduits 103 which are arranged uniformly spaced about thecylinder 102. Each pressure conduit 103 leads to a nonillustrated fuelinjection valve of the internal combustion engine. The number of thepressure conduits 103 is equal to that of the cylinders of the internalcombustion engine which is served by the fuel injection pump. In thecylinder 102 the pump piston 101 bounds a pump work chamber 106 whichduring the suction stroke of the pump piston is supplied with fuel fromthe suction chamber 111 through longitudinal grooves 109 provided in thelateral face of pump piston 101 and a supply channel 110. Thelongitudinal grooves 109 are equal in number to that of the pressureconduits 103 and merge into the pump work chamber 106.

From the pump work chamber 106 there extends a bore 141 which mergesinto a compartment 142. The mouth of the bore 141 is formed as a valveseat and is closable by a valve body 143 which is loaded by a spring 144accommodated in the compartment 142. From the latter there extends aconduit 145 which merges into the cylinder 102 in a plane situatedbetween the entry of the supply channel and the entry of the pressureconduits 103 into the cylinder 102.

The pump piston 101 has an annular groove 108 which communicates with alongitudinal distributor groove 105 provided on the lateral face of thepump piston 101. For each pressure stroke of the pump piston 101 adifferent pressure conduit 103 is connected with the conduit through thedistributor groove 105. The latter can be connected with one of thepressure conduits 103 only if the longitudinal grooves 109 are not incommunication with the supply conduit 110.

The pump piston 101 has an axial blind bore 107 which at one endcommunicates with the pump work chamber 106 and at the other end isintersected by a radially extending throughgoing bore 146. In the zoneof the latter there is disposed a control sleeve 118 which is slidablymounted in a fluid-tight manner on the piston 101. Dependent upon theposition of the control sleeve 1 18, during the pressure strokes of thepump piston the bore 146 is opened by the upper edge 118a of the controlsleeve 118 at an earlier or later moment so that a certain variableresidual quantity of the delivered fuel may flow into the suctionchamber 111 from the pump work chamber 106 through the bores 107, 146.In case the control sleeve 118 is set in such a manner that the bore 146is not uncovered at all during the pressure strokes of the pump piston101, then the entire fuel quantity delivered by the pump piston(excessive fuel quantity for engine start) will be directed into thepressure conduits 103. The displacement of the control sleeve 118 iseffected by a lever 148 which is pivotable about a stationary point 149and has a nose 150 which projects into a depression 151 provided in thecontrol sleeve 118. The lever 148 is displaceable as a function of loadand rpm by means not shown.

In order to obtain in the suction chamber 111 an rpm-dependent pressure,the fuel supply is effected in the same manner as described inconnection with the first embodiment in FIG. 1 through a pump 112 whilethe pressure of the suction chamber is regulated by means of a piston116 which is loaded by a spring 117 and which controls a throttle 115situated in a return channel 114.

According to the invention, in the fuel injection pump illustrated inFIG. 7, there is provided on the piston 101, immediately adjacent theopening of the bore 146, a ground portion which constitutes a throttle136. In this manner, during each pressure stroke of the piston 110 thepump work chamber is first discharged through the throttle 136 and then,after an additional axial displacement of the pump piston 101, it isdischarged through the bore 146. Thus, there is obtained, in a mannersimilar to that already discussed in connection with the type of pumpshown in FIG. 1, an adaptation of the fuel injection quantities as afunction of the rpm, particularly in the low rpm range.

Turning now to FIG. 8 there is shown an elevational view of that side ofthe pump piston 101 which contains the throttle 136 and the outlet planeof the bore 146. In this embodiment the plane of the ground portion 136is at an angle with respect to the longitudinal axis of the pump piston101; it is to be understood that the throttle may be formed as a groundportion which is parallel to the longitudinal axis of the pump piston.Further, the throttle may also be provided on the inner lateral face ofthe control sleeve 118 in the vicinity of the upper control edge. Thissolution, however, involves more complex machining. The arrangement andformation of the throttle described in connection with FIGS. 4 and 5 mayalso be adapted in case of the piston illustrated in FIG. 8.

It is thus seen that in fuel injection pumps in which the injectedquantities are controlled by sliding elements which regulate a bypass,there is achieved in the low rpm range for any load a reduction of theinjected fuel quantities by providing a throttle at a particularlocation by simple means. The course of the injected fuel quantity as afunction of the rpm is determined by the particular shape of thethrottle. At higher rpms there may be obtained, however, the originallevel of injection since, as the rpm increases, the fuel quantitieswhich pass through the throttle are decreased.

What is claimed is:

1. In a fuel injection pump of the known type that has (a) areciprocating pump piston, (b) a pump work chamber bounded by said pumppiston, pressure conduit means through which fuel is forced from saidpump work chamber by said pump piston during its pressure strokes, (d) abypass channel leading from said pump work chamber, (e) a slidable fuelquantity regulator member having control edge means for opening saidbypass channel at an rpm-dependent moment during said pressure strokesfor interrupting fuel delivery to said pressure conduit means during aportion of each pressure stroke by causing fuel to escape from said pumpwork chamber through said bypass channel and (f) means for displacingsaid fuel quantity regulator member to an rpm-dependent extent, theimprovement comprising a throttle in the surface of said regulatormember between said control edge means and said bypass channel whenviewed in the direction of the relative opening motion of said fuelquantity regulator member and at least partially contiguous to saidcontrol edge means; during the relative opening motion between saidbypass channel and said fuel quantity regulator member said bypasschannel being opened first through said throttle and subsequently bysaid control edge means.

2. An improvement as defined in claim 1, wherein said throttle isconstituted by a recessed ground portion extending parallel to and beingaxially bounded by said control edge means.

3. An improvement as defined in claim 1, wherein said throttle isconstituted by a bore through which said bypass channel is opened priorto being opened by said control edge means during said relative motion.

4. An improvement as defined in claim 3, wherein said bore constitutingsaid throttle is provided in said fuel quantity regulator member, saidbore having a first open end disposed at said control edge means and asecond open end situated downstream of said control edge means whenviewed in the direction of the relative opening motion of said fuelquantity regulator member.

5. An improvement as defined in claim 1, including A. a regulatorshuttle constituting said fuel quantity regulator member,

B. an auxiliary piston operating synchronously with said pump piston,

C. first channel means containing hydraulic liquid and leading from saidauxiliary piston to said regulator shuttle for causing the latter toexecute forward strokes in response to the pressure strokes of saidauxiliary piston,

D. means exerting a return force on said regulator shuttle for causingthe latter to execute return strokes during the suction strokes of saidauxiliary piston,

E. second channel means leading from said regulator shuttle, said secondchannel means carrying at least part of the hydraulic liquid displacedby said regulator shuttle during its return strokes,

F. an adjustable restriction disposed in said second channel means tobrake said regulator shuttle during its return strokes; beyond an enginerpm determined by the setting of said adjustable restriction the brakingeffect of said hydraulic liquid in said second channel means causes theappearance of a fluid abutment preventing said regulator shuttle toreturn, during its reciprocating motion, into its original position ofrest,

G. an axially parallel shutoff groove provided in the lateral face ofsaid regulator shuttle, said shut-off groove, when aligned with saidbypass channel by virtue of rotating said regulator shuttle into apredetermined angular position maintains communication between said pumpwork chamber and said bypass channel in any position of said regulatorshuttle and [-1. an annular groove provided on said regulator shuttledownstream of said control edge means when viewed in the direction ofthe pressure strokes of said regulator shuttle, said annular grooveconstituting said throttle and continuously communicating with saidbypass channel through said axially parallel shutofi' groove.

6. An improvement as defined in claim l, including A. a regulatorshuttle constituting said fuel quantity regulator member,

B. an auxiliary piston operating synchronously with said pump piston,

C. first channel means containing hydraulic liquid and leading from saidauxiliary piston to said regulator shuttle for causing the latter toexecute forward strokes in response to the pressure strokes of saidauxiliary piston,

D. means exerting a return force on said regulator shuttle for causingthe latter to execute return strokes during the suction strokes of saidauxiliary piston,

E. second channel means leading from said regulator shuttle, said secondchannel means carrying at least part of the hydraulic liquid displacedby said regulator shuttle during its return strokes,

F. an adjustable restriction disposed in said second channel means tobrake said regulator shuttle during its return strokes; beyond an enginerpm determined by the setting of said adjustable restriction the brakingeffect of said hydraulic liquid in said second channel means causes theappearance of a fluid abutment preventing said regulator shuttle toreturn, during its reciprocating motion, into its original position ofrest,

G. a recessed portion provided on said regulator shuttle downstream ofsaid control edge means when viewed in the direction of the pressurestrokes of said regulator shuttle, said recessed portion constitutingsaid throttle,

H. an additional bypass channel extending from said first channel meansand being normally closed by said regulator shuttle,

I. an axially parallel groove provided in the lateral face of saidregulator shuttle, said groove, when aligned with said additional bypasschannel by virtue of rotating said regulator shuttle into apredetermined angular position, maintains communication between saidfirst channel means and said additional bypass channel to cause adischarge of the hydraulic liquid pressurized by said auxiliary pistonfor effecting the injection of excess fuel quantities for starting acold engine; said control edge means and said recessed portion on saidregulator shuttle being out of alignment with said bypass channel at anyposition of said regulator shuttle when said groove is in alignment withsaid additional bypass channel.

7. In a fuel injection pump of the known type that has (a) areciprocating pump piston, (b) a pump work chamber bounded by said pumppiston, (0) pressure conduit means through which fuel is forced fromsaid pump work chamber by said pump piston during its pressure strokes,(d) a bypass channel leading from said pump work chamber, (e) a slidablefuel quantity regulator member having control edge means for openingsaid bypass channel at an rpm-dependent moment during said pressurestrokes for interrupting fuel delivery to said pressure conduit meansduring a portion of each pressure stroke by causing fuel to escape fromsaid pump work chamber through said bypass channel and (f) means fordisplacing said fuel quantity regulator member to an rpm-dependentextent, the improvement comprising a throttle formed contiguous with anopening end of said bypass channel; during the relative opening motionbetween said bypass channel and said fuel quantity regulator member saidbypass channel being opened first through said throttle and subsequentlyby said control edge means.

8. An improvement as defined in claim 7 including a component thatcontains at least part of said bypass channel, said throttle beingsituated on said component upstream of said bypass channel when viewedin the direction of the relative opening motion of said fuel quantityregulator member.

9. An improvement as defined in claim 8 wherein said throttle isconstituted by a recessed ground portion bounding said bypass channel.

1. In a fuel injection pump of the known type that has (a) areciprocating pump piston, (b) a pump work chamber bounded by said pumppiston, (c) pressure conduit means through which fuel is forced fromsaid pump work chamber by said pump piston during its pressure strokes,(d) a bypass channel leading from said pump work chamber, (e) a slidablefuel quantity regulator member having control edge means for openingsaid bypass channel at an rpm-dependent moment during said pressurestrokes for interrupting fuel delivery to said pressure conduit meansduring a portion of each pressure stroke by causing fuel to escape fromsaid pump work chamber through said bypass channel and (f) means fordisplacing said fuel quantity regulator member to an rpmdependentextent, the improvement comprising a throttle in the surface of saidregulator member between said control edge means and said bypass channelwhen viewed in the direction of the relative opening motion of said fuelquantity regulator member and at least partially contiguous to saidcontrol edge means; during the relative opening motion between saidbypass channel and said fuel quantity regulator member said bypasschannel being opened first through said throttle and subsequently bysaid control edge means.
 2. An improvement as defined in claim 1,wherein said throttle is constituted by a recessed ground portionextending parallel to and being axially bounded by said control edgemeans.
 3. An improvement as defined in claim 1, wherein said throttle isconstituted by a bore through which said bypass channel is opened priorto being opened by said control edge means during said relative motion.4. An improvement as defined in claim 3, wherein said bore constitutingsaid throttle is provided in said fuel quantity regulator member, saidbore having a first open end disposed at said control edge means and asecond open end situated downstream of said control edge means whenviewed in the direction of the relative opening motion of said fuelquantity regulator member.
 5. An improvement as defined in claim 1,including A. a regulator shuttle constituting said fuel quantityregulator member, B. an auxiliary piston operating synchronously withsaid pump piston, C. first channel means containing hydraulic liquid andleading from said auxiliary piston to said regulator shuttle for causingthe latter to execute forward strokes in response to the pressurestrokes of said auxiliary piston, D. means exerting a return force onsaid regulator shuttle for causing the latter to execute return strokesduring the suction strokes of said auxiliary piston, E. second channelmeans leading from said regulator shuttle, said second channel meanscarrying at least part of the hydraulic liquid displaced by saidregulator shuttle during its return strokes, F. an adjustablerestriction disposed in said second channel means to brake saidregulator shuttle during its return strokes; beyond an engine rpmdetermined by the setting of said adjustable restriction the brakingeffect of said hydraulic liquid in said second channel means causes theappearance of a fluid abutment preventing said regulator shuttle toreturn, during its reciprocating motIon, into its original position ofrest, G. an axially parallel shutoff groove provided in the lateral faceof said regulator shuttle, said shut-off groove, when aligned with saidbypass channel by virtue of rotating said regulator shuttle into apredetermined angular position maintains communication between said pumpwork chamber and said bypass channel in any position of said regulatorshuttle and H. an annular groove provided on said regulator shuttledownstream of said control edge means when viewed in the direction ofthe pressure strokes of said regulator shuttle, said annular grooveconstituting said throttle and continuously communicating with saidbypass channel through said axially parallel shutoff groove.
 6. Animprovement as defined in claim 1, including A. a regulator shuttleconstituting said fuel quantity regulator member, B. an auxiliary pistonoperating synchronously with said pump piston, C. first channel meanscontaining hydraulic liquid and leading from said auxiliary piston tosaid regulator shuttle for causing the latter to execute forward strokesin response to the pressure strokes of said auxiliary piston, D. meansexerting a return force on said regulator shuttle for causing the latterto execute return strokes during the suction strokes of said auxiliarypiston, E. second channel means leading from said regulator shuttle,said second channel means carrying at least part of the hydraulic liquiddisplaced by said regulator shuttle during its return strokes, F. anadjustable restriction disposed in said second channel means to brakesaid regulator shuttle during its return strokes; beyond an engine rpmdetermined by the setting of said adjustable restriction the brakingeffect of said hydraulic liquid in said second channel means causes theappearance of a fluid abutment preventing said regulator shuttle toreturn, during its reciprocating motion, into its original position ofrest, G. a recessed portion provided on said regulator shuttledownstream of said control edge means when viewed in the direction ofthe pressure strokes of said regulator shuttle, said recessed portionconstituting said throttle, H. an additional bypass channel extendingfrom said first channel means and being normally closed by saidregulator shuttle, I. an axially parallel groove provided in the lateralface of said regulator shuttle, said groove, when aligned with saidadditional bypass channel by virtue of rotating said regulator shuttleinto a predetermined angular position, maintains communication betweensaid first channel means and said additional bypass channel to cause adischarge of the hydraulic liquid pressurized by said auxiliary pistonfor effecting the injection of excess fuel quantities for starting acold engine; said control edge means and said recessed portion on saidregulator shuttle being out of alignment with said bypass channel at anyposition of said regulator shuttle when said groove is in alignment withsaid additional bypass channel.
 7. In a fuel injection pump of the knowntype that has (a) a reciprocating pump piston, (b) a pump work chamberbounded by said pump piston, (c) pressure conduit means through whichfuel is forced from said pump work chamber by said pump piston duringits pressure strokes, (d) a bypass channel leading from said pump workchamber, (e) a slidable fuel quantity regulator member having controledge means for opening said bypass channel at an rpm-dependent momentduring said pressure strokes for interrupting fuel delivery to saidpressure conduit means during a portion of each pressure stroke bycausing fuel to escape from said pump work chamber through said bypasschannel and (f) means for displacing said fuel quantity regulator memberto an rpm-dependent extent, the improvement comprising a throttle formedcontiguous with an opening end of said bypass channel; during therelative opening motion between said bypass channel and said fuelquantiTy regulator member said bypass channel being opened first throughsaid throttle and subsequently by said control edge means.
 8. Animprovement as defined in claim 7 including a component that contains atleast part of said bypass channel, said throttle being situated on saidcomponent upstream of said bypass channel when viewed in the directionof the relative opening motion of said fuel quantity regulator member.9. An improvement as defined in claim 8 wherein said throttle isconstituted by a recessed ground portion bounding said bypass channel.